1. Field of the Invention
This invention relates to manual resuscitator systems. More specifically, this invention relates to resuscitation bags having directional control valves and means for controling the "PEEP" or Positive End Expiratory Pressure.
2. Description of Related Art including Information Disclosed under .sctn..sctn.1.97 to 1.99
Manual cardiopulmonary resuscitation devices, utilizing self-inflating squeeze bags are well known in the prior art. An example, for instance, is shown in U.S. Pat. No. 4,774,941 which issued Oct. 4, 1988, to Wallace F. Cook. Also, there are earlier patents. Representative examples are:
U.S. Pat. No. 3,009,459 issued Nov. 21, 1961 to Henning Ruben PA0 U.S. Pat. No. 3,262,446 issued Jul. 26, 1966 to George H. Stoner PA0 U.S. Pat. No. 4,037,595 issued Jul. 26, 1977 to James O. Elam PA0 U.S. Pat. No. 4,077,404 issued Mar. 7, 1978 to James O. Elam PA0 U.S. Pat. No. 4,088,131 issued May 9, 1978 to James O. Elam et al PA0 U.S. Pat. No. 4,121,580 issued Oct. 24, 1978 to Donald C. Fabish PA0 U.S. Pat. No. 4,239,038 issued Dec. 16, 1980 to Ronald W. Holmes PA0 U.S. Pat. No. 4,374,521 issued Feb. 22, 1983 to Thomas W. Nelson et al
During resuscitation with such devices, air or air enriched with oxygen is forced into the patient by squeezing the bag. The patient exhales through the valving system of the device. On release of the squeeze bag, the bag reinflates through a check valve. In addition to possessing the potential to force the desired flow and quantity of gases to the patient, such devices must take into account the fact that the patient may inhale or exhale spontaneously during treatment. These devices are therefore usually comprised of three basic elements: a mask, a specific directional control valve arrangement, and a squeezable bag.
These three elements have been well documented in the prior art. The mask must have sufficient flexibility to adjust to the contours of the face, while maintaining sufficient rigidity to allow for the application of enough force to create a seal during the direction of gas flow under pressure. The directional control valve must allow air to be forced under pressure to the patient, while still, as stated, allowing the patient to spontaneously inhale and exhale. An example of such a directional control valve is disclosed in U.S. Pat. No. 3,556,122 which issued Apr. 1971 to Asmund S. Laerdal.
Finally, the squeeze bag typically incorporates a check valve allowing air to fill the bag and must be of such construction as to be sufficiently compliant to allow 40 cycles per minute of operation while delivering a minimum of 500 cc. of air per cycle at 100 cm. of water pressure.
In addition to these three basic elements necessary to achieve the essential functions of cardiopulmonary resuscitation, there is frequently added a fourth element which is an external valve to provide measured and controllable resistance to the exhaled airflow, whether part of a forced cycle or spontaneous respiration. This element is known as a PEEP valve. The acronym PEEP as used in this case represents the term Positive End Expiratory Pressure, which is the aforementioned resistance to exhaled airflow at the preset pressure. The application of PEEP has long been recognized as a benefit to patients of cardiopulmonary resuscitation by maintaining a degree of inflation in the lungs, thus enabling a prolonged contact between the inhaled gases and the subject's pulmonary capillary bed, and preventing collapse of the lung.
In the past PEEP control valves have usually been separate from the air supply valve. The early U.S. Pat. No. 1,244,661 to Teter issued Oct. 30, 1917 discloses a mask provided with a valve for controlling the pressure during exhalation. The patent teaches that the device provides a "positive, adjustable pressure-valve" in order "to increase the absorption by the blood of the anesthetizing gas or vapors, and the lungs will not suffer collapse but may be distended thereby."
Another U.S. Pat. No. 1,896,716 to Elmer I. McKesson issued Feb. 7, 1933 discloses a mask having an exhaling valve with spring force adjustable by set screw to control exhalation pressure.
U.S. Pat. No. 3,710,780 issued Jan. 16, 1973 to Robert A. Milch has the patient exhale through a tube, the far end of which is dipped into water to an adjustable extent to control the exhalation pressure required.
The phrase "Positive End Expiratory Pressure" is used in the British patent 1,447,091 (1976) wherein a diaphram normally blocks the exhaust seat. A threaded nut with graduations adjusts the pressure on a spring to push the diaphragm against the seat to thereby adjust the amount of pressure required to exhaust the valve.
In the U.S. Pat. No. 4,182,366 issued Jan. 8, 1980 to John R. Boehringer a spring urges a diaphram to close an exhaust port. This patent uses the acronym "PEEP". A thumb screw can be adjusted to control the pressure on the spring.
The PEEP valve shown in U.S. Pat. No. 4,207,884 to Max Isaacson issued Jun. 17, 1980 comprises an annular seat and a disk-shaped valve. A spring urges the valve against its seat in accordance with the setting on a graduated plunger.
Two U.S. Pat. Nos. Re. 32,553 issued Dec. 30, 1980 to Clifford D. Bennett et al and 4,712,580 issued Dec. 15, 1987 to Keith Gilmanm et al are both directed to PEEP valves in which the opening of the exhaust valve is effected when the exhaling pressure raises the diaphram central of the valve to permit escape of air into the valve exhaust. The diaphragm is urged against the valve seat in each case by air pressure communicated through a tubular opening in the valve housing.
U.S. Pat. No. 4,345,593 issued Aug. 24, 1982 to John L. Sullivan and U.S. Pat. No. 4,433,685 issued Feb. 24, 1984 to Eugene A. Giorgini et al both include as a part of a mask an adjustible exit valve which would control PEEP (see FIG. 3 of both patents).
The U.S. Pat. No. 4,870,963 issued Oct. 3, 1989 to William Carter discloses a PEEP valve in which a valve element is pivotally mounted on a hub so that if one side of the valve is blocked, the valve can pivot open. Spring pressure is adjustable by turning a plunger.
While each of the four elements discussed above are recognized by the prior art, the prior art has perceived the resuscitation bag system with its valving as necessarily separate from the PEEP valve. The use of an external PEEP valve presents an inconvenience in emergency situations in which the resuscitation device is typically required. Its use also increases the cost of therapy and may be found to provide less effective therapy because there are two valves in the path of exhaled gases. First, the gases must pass through the aforementioned directional control valve integral to the resuscitation bag system known from the prior art. Then the exhaled gases must pass through the PEEP valve. This dual valving can potentially increase the resistance to exhaled gases in an unpredictable manner in the normal course of therapy and is therefore potentially detrimental.